JavaCard

Java Card technology provides a secure environment for the execution of applications on Smart Card-s and other devices with limited memory and processing capabilities.

http://java.sun.com/products/javacard/

http://java.sun.com/products/javacard/faq.html

http://www.javacardforum.org/About_JCF/about_jcf.html

http://www.opencard.org/

does it use Open Standards?

If I already have a GSM Cell Phone with a SIM card, what does a JavaCard buy me in terms of Digital Identity?